OpenAthens is described as 'The world of libraries, librarians and information professionals is in a period of exciting transition. As libraries, technology and information evolve, there is one constant: people want information that supports their learning, development and decision making'. There are three alternatives to OpenAthens for Self-Hosted solutions, Windows, Linux, Mac and Online / Web-based. The best alternative is CAS, which is both free and Open Source. Other great apps like OpenAthens are shibboleth (Free, Open Source) and SimpleSAMLphp (Free, Open Source).
standards based, open source software for web single sign-on across or within organizational boundaries allowing sites to make informed authorization decisions for individual access of protected online resources in a privacy-preserving manner.
SimpleSAMLphp is an application written in native PHP that deals with authentication. The main focus of SimpleSAMLphp is providing support for SAML 2.0 as a Service Provider (SP) and SAML 2.0 as an Identity Provider (IdP).